The exhaust gas recirculating (EGR) valve is an important part of the emissions control system of the modern automotive vehicle. It is also a fairly expensive component. However, most garages and repair shops are not equipped to test the operation of EGR valves because those valves rely upon vacuum or vacuum and pressure for their operation. The ones that require both vacuum and pressure respond to a low pressure to close a pilot valve to permit a diaphragm to respond to a vacuum. Under present circumstances, if an automobile, for example, fails to pass an emissions test, it is not uncommon for the garage or repair shop simply to replace the EGR valve for want of a means for testing the old one.
An EGR valve has a flat mounting surface, and a domed vacuum chamber, a lower wall of which is formed by a movable diaphragm. A vacuum fitting projects from the dome, for connection to a hose communicating with the intake manifold. Most of the EGR valves have a passage in the flat mounting surface communicating with a plunger type valve stem, which moves up in response to pressure from the exhaust manifold to close an opening in the diaphragm, so that, until pressure is built up in the exhaust manifold, the diaphragm will not move to open the EGR valve. The domed chamber and diaphragm are frequently supported by a kind of spider, which leaves at least a part of the diaphragm visible from below.
One of the objects of this invention is to provide a test fixture for EGR valves that will accommodiate all presently used standard EGR valves, and which can be used with the equipment commonly found in garages and repair shops.
Another object is to provide such a test fixture that is simple, economical, safe, effective and easy to use.
Other objects will become apparent to those skilled in the art in the light of the following description and accompanying drawing.